In recent years, more and more information terminals employ a touch panel as an input device. Since a touch panel can be arranged so as to be overlaid on a display panel, it has been the mainstream of input devices particularly in mobile information terminals, for the reason that the screen can be expanded therewith.
Meanwhile, a touch panel can give feedback on a user operation and present information in accordance with an operation, only by presenting some kind of information on the screen. For this reason, the user cannot obtain information other than the displayed information, and it is difficult for the user to recognize which part of the screen he/she is touching. Accordingly, the touch panel has a problem in that it is difficult for the user to perform an operation.
To address this problem, a device has been proposed that enables physical feedback to be provided to a fingertip of a user, that is, a device that enables a tactile force sense to be presented (transmitted) (e.g., see Patent Documents 1 and 2). Specifically, the device disclosed in Patent Document 1 includes a mechanism that enables a display panel provided on a screen of a touch panel to be moved along a thickness direction of the display panel. With the device disclosed in Patent Document 1, the aforementioned mechanism can move the display panel in accordance with a finger touch by a user, and accordingly a tactile force sense can be presented to the user.
Patent Document 2 proposes a device that presents a tactile sense to a fingertip of a user by vibrating a touch panel, using a piezoelectric actuator (e.g., see Patent Document 2). The device disclosed in Patent Document 2 is configured by overlaying a transparent panel, in which the piezoelectric actuator is embedded, on the touch panel and a display panel.
However, with the device disclosed in Patent Document 1, since the entire touch panel needs to be operated, the structure becomes complicated and the size and weight of the device itself consequently increases. For this reason, it is difficult to mount the device disclosed in Patent Document 1 in a mobile terminal such as a smartphone or a tablet.
On the other hand, it is considered that the device disclosed in Patent Document 2 will be able to be mounted in a mobile terminal, since an increase in the size and weight of the device is avoided, unlike the device disclosed in Patent Document 1. However, with the device disclosed in Patent Document 2, the range of displacement is small, only tactile sense presentation using a vibration can be performed, and furthermore, expressiveness of tactile force presentation using a vibration is poor. Therefore, the device disclosed in Patent Document 2 is not suitable for content that requires successive changes and accuracy.
Incidentally, it is considered that the problem in Patent Document 2 can be solved with the device disclosed in Patent Document 1. Accordingly, for example, if the size of the actuator used for moving the touch panel and the display panel can be reduced in the device disclosed in Patent Document 1, both of the aforementioned two problems can be solved at a time, and it is considered that the device can be mounted in a mobile terminal.